As you should know already, the WebM project is dedicated to developing a high-quality, open video format for the web that is freely available to everyone. Latest Open Shot 1.2.2 now has an option to export your videos in WebM format.
OpenShot Adds WebM Support
The WebM format is a combination of a new video codec sponsored by Google called "VP8" and the "Vorbis" audio codec. The container format ends with a ".webm" extension. As the developer points out, OpenShot does not have a "Simple" profile for WebM yet, you can still use it, if you know how.
To use WebM, you must have version 0.6+ of FFmpeg (which is included in Ubuntu 10.10). For those using older versions of Ubuntu, you will have to upgrade to the latest version of FFmpeg to get this OpenShot feature working. [via openshot]